Molecular characterization of ribonucleic acid from Escherichia coli ribosomes : I. Isolation and molecular weights

Abstract

The ribonucleic acid from purified 30 s, 50 s and 70 s ribosomes of E. coli has been isolated by the phenol and detergent methods. Both isolation procedures give the same results. The 30 s ribosomes contain 16 s ribonucleic acid, while the 50 s and 70 s particles yield a mixture of 16 s and 23 s ribonucleic acids in varying proportions. A combination of light scattering and hydrodynamic measurements was used to calculate the molecular weights of the ribonucleic acid. Values of 5·6 × 105 and 1·1 × 106 were obtained for the 16 s and 23 s components, respectively. Since the 30 s ribosome has a molecular weight of approximately 8 × 105 and is 63% ribonucleic acid, it must contain one 16 s unit. The 1·8 × 106 molecular weight 50 s ribosomes also contain 63% ribonucleic acid. It is suggested that they are heterogeneous; some contain one 23 s ribonucleic acid component, while others contain two 16 s units.